JPH0992492A - Plasma generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plasma generator which provides a high-density plasma. SOLUTION: This microwave type plasma generator has between a microwave guide 3 and a vacuum vessel 1 a dielectric pipe 6 and an antenna 7 surrounding the dielectric pipe 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma generator, for example, a plasma generator for a large area process, a linear ion source, a large area oxide film generator for metal or the like, a surface treatment device for a film or the like, a plasma accelerator. The present invention is useful for general applications to plasma-using devices such as plasma etching devices, and is suitable as a plasma generating device such as an etching device, a sputtering device, a thin film forming device, etc. that needs to be processed efficiently in a short time.

[0002]

2. Description of the Related Art A conventional sheet plasma generator is shown in FIG. FIG. 4 shows a so-called microwave type sheet plasma generator which absorbs microwaves into gas to generate plasma. (A) is a side structure (b) is A of (a)
-B cross section. In FIG. 4, the microwave 9 transmitted through the rectangular cross-section waveguide 3 is made incident on the metal tube 5 through the entrance window 4 having the same cross-section as the waveguide 3, and the microwave is generated in the metal tube 5. The plasma is generated in a sheet shape while controlling the propagation of No. 9. Here, the plasma is generated by the coil 2 which is arranged outside the vacuum container 1 and creates a magnetic field B _0.
In the ECR zone E generated by, the microwave 9 incident in parallel with the magnetic field B ₀ is efficiently absorbed under the ECR condition while propagating in the metal tube 5 having a rectangular cross section, so that the sheet plasma P ₀ is generated. To do. In addition, ECR
Conditions and ECR of ECR zone are Electron Cycrotron
Resonance (Electron cyclotron resonance), in which the electrons in the magnetic field make rotational motion at the cyclotron frequency, but when an electromagnetic wave vibrating at the same frequency as this frequency acts on the electrons in the plasma, the electromagnetic waves can convert the energy into electron kinetic energy, is that the resonance phenomenon. plasma P ₀ generated in the coils 2
The axial magnetic field B ₀ causes the plasma to be transported to the target 8 in the vacuum container 1 and confine the plasma.

[0003]

In the sheet plasma generator, that is, the microwave plasma generator according to the above description, the plasma density depends on control parameters such as gas pressure, magnetic field strength, and microwave power. Among the parameters, the plasma tightening due to the increase of the magnetic field strength is limited due to the limitation of the ECR condition and the power consumption in the coil, and the increase of the density due to the increase of the gas pressure is limited considering the plasma transport efficiency. . Further, the increase of microwave power contributes to the increase of density without changing the shape of the sheet plasma and without limitation of other factors, but the increase rate of the plasma density with respect to the microwave power is constant. When it becomes above, there is a tendency to be saturated, and this also has a limit. Then, for example, in order to increase the plasma density by 10 times, microwave power of 100 times or more is required.

In view of the above problems, it is an object of the present invention to provide a plasma generator having a higher plasma density.

[0005]

The present invention which achieves the above-mentioned objects has the following objects. (1) A vacuum container, a waveguide for transmitting microwaves, and an entrance window having the same shape as the waveguide cross section provided at the end of the waveguide,
A metal tube provided in contact with the entrance window, a dielectric tube having a cross section of the same shape as the cross section of the metal tube installed between the metal tube and the vacuum vessel, and an antenna surrounding the dielectric tube. It is characterized by comprising a coil arranged so as to surround the vacuum container and the metal tube portion. (2) In (1), a plurality of waveguides arranged in parallel are
It is characterized in that it is provided on the metal tube through a plurality of entrance windows. (3) In (1), the cross-sectional shape of the metal tube is rectangular. (4) In (1), the coil is arranged so as to surround the metal tube so that a part of the cross section of the metal tube is cut out.

A high frequency electric field of MH _Z order, for example, is generated by an antenna surrounding the dielectric tube with respect to plasma (hereinafter referred to as “matrix plasma”) generated in the metal tube in the ECR zone, and this high frequency electric field and the axial magnetic field by the coil are generated. A helicon wave that causes a high-frequency current to flow around the plasma in the dielectric tube container (an electromagnetic wave that propagates parallel to the magnetic field in the plasma, and a Whistler wave whose phase velocity changes with frequency or wavelength (Low-frequency part) is excited, and the plasma density achieved by this host plasma is EC
A plasma having a density equal to or higher than R discharge is obtained. Here, a helicon wave is excited by a high-frequency electric field generated by an antenna that surrounds the space and an axial magnetic field generated by a coil. An increase in the high-frequency power that surrounds the maternal plasma due to the helicon wave increases the maternal plasma density and makes the plasma groove constant. When it exceeds the value, a density jump occurs and a plasma density higher than the ECR discharge is obtained. In this case, when the plasma density exceeds a certain value, the density jump is caused by a wave excited by an antenna exciting a helicon wave in the plasma without loss and generating high energy electrons (about several ev). In this density jump, since the density jump is induced by the helicon wave on the premise of the density achieved by the mother plasma, the microwave power does not need to be enormous. As a result, a high density plasma can be obtained without disturbing the plasma shape without requiring enormous microwave power.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will now be described with reference to FIGS. 1 and 2 show one embodiment, FIG. 1 (a) is a side surface configuration (b) is an AB cross section of (a), FIG. 2 (a) is a metal pipe side surface, and (b) is (a). Bottom of the
2C shows a side surface of the antenna and the dielectric tube, FIG. 2D shows a bottom surface thereof, and FIG. 2E shows a front surface thereof, and the same portions as those in FIG. 1 and 2 show a high density sheet plasma generator. In FIG. 1, 1 is a rectangular (or circular) vacuum container, 2 is a coil for forming an axial magnetic field and ECR zone E, 3 is a microwave transmission waveguide, 4 is an entrance window, and 5 is an ECR plasma shape. A shaping metal tube for control, 8 is a target.

A dielectric tube 6 for exciting a helicon wave for densifying the mother plasma and a loop-shaped high frequency antenna 7 surrounding the dielectric tube 6 are arranged between the vacuum container 1 and the metal tube 5. To be done. Here, in order to generate the sheet plasma, there is provided a metal tube 5 as shown in FIGS. 2 (a) and 2 (b), and a plasma emission port m is provided to an incident window 4 made of a vacuum holding derivative of the microwave 9. It is possible to generate sheet plasma narrowed down in the thickness direction t by making the rectangle narrow in the thickness direction t. In this case, the incident window 4 has the same shape as the cross section of the microwave waveguide 3, and therefore there is no problem of discharge breakdown on the atmosphere side of the incident window 4 even when high power is incident.

Further, as shown in FIGS. 2 (c), (d) and (e), a dielectric tube 6 having the same cross section as the metal tube 5 is provided at the end of the metal tube 5, and the dielectric tube prevents reflection of high frequencies. Tube 6
Here, a rectangular ring-shaped antenna 7 is provided so as to surround the. In this case, the antenna 7 does not surround the entire cross section of the dielectric tube 6 and is partially cut out as shown in FIG. Further, the antenna 7 has a magnetic field direction B _0.
A plurality of units may be installed electrically in series or in parallel in the direction parallel to. The radio frequency electric field generated by the antenna 7 and the axial magnetic field generated by the coil 2 cause the matrix plasma density to satisfy the helicon wave dispersion relationship, so that a helicon wave having a rectangular cross section is excited in the sheet plasma.

The microwave introduced from the waveguide 3 is in contact with the entrance window 4 and the inside of the metal tube 5 is evacuated to ECR.
A sheet plasma P ₀ that propagates to the zone (E) and serves as a matrix in the metal tube 5 is generated. Generated maternal plasma P
_A rectangular cross-section mode helicon wave is excited by setting a rectangular ring type high frequency antenna 7 for helicon wave excitation and a magnetic field condition in the axial direction suitable for helicon wave excitation at that position by the power of the helicon wave. The density jump is induced by slightly increasing the density from the achieved density of the mother plasma, and the high density sheet plasma P ₁ is generated.

FIG. 3 shows an example for increasing the size of the apparatus and sheet plasma. As shown in the figure, microwaves 9 are introduced into the vacuum container 1 in parallel through a plurality of incident windows, and the metal tube 5 and the helicon wave exciting rectangular ring type high frequency antenna 7 are made common with long sides. It is possible to generate high density sheet plasma P ₁ having an arbitrary width.

[0012]

As described above, according to the present invention, the microwave is introduced into the metal tube through the entrance window by the waveguide, the microwave propagation is controlled by the metal tube, and the coil is installed outside the vacuum container. Plasma is generated in the metal tube with high efficiency by using the ECR condition generated in 1., and the helicon wave is excited in the plasma by the ring-shaped antenna installed on the outer periphery of the dielectric connected to the end of the metal tube, By using the achieved density of the above plasma to induce a density jump, by superimposing a helicon wave by a ring type high frequency antenna to induce a density jump, a high density that cannot be achieved with the same microwave power as the total input power. It has been possible to obtain a method for generating plasma with extremely high efficiency.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is a configuration diagram of a metal tube and a dielectric tube antenna.

FIG. 3 is a configuration diagram of another example of the present invention.

FIG. 4 is a configuration diagram of a conventional example.

[Explanation of symbols]

 1 vacuum container 2 coil 3 waveguide 4 entrance window 5 metal tube 6 dielectric tube 7 antenna 8 target

Claims (4)

[Claims] 1. A vacuum container, a waveguide for transmitting microwaves, an entrance window having the same shape as the waveguide cross section provided at an end of the waveguide, and a metal tube provided in contact with the entrance window. A dielectric tube having a cross section of the same shape as the cross section of the metal tube installed between the metal tube and the vacuum container; an antenna surrounding the dielectric tube; and surrounding the vacuum easy and metal tube parts. A plasma generator comprising: arranged coils. 2. The metal tube is provided with a plurality of waveguides arranged in parallel through a plurality of entrance windows.
The plasma generator according to the above. 3. The plasma generator according to claim 1, wherein the cross section of the metal tube is rectangular. 4. The plasma generator according to claim 1, wherein the coil is arranged so as to surround the metal tube so as to cut out a part of the cross section of the metal tube.